I don't think they really said anything horrible, in all honesty I can't believe anybody would ever say "because I know you're not invited anywhere" I think op just exaggerated in the FML. But I doubt that's how it actually went down.

If you weren't doing anything, babysit all of the kids at once. When your 'friends' ask why there were so many other kids, ask why so many people thought you were free instead of asking you out with them. Also, charge a lot of money.